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By E. A. Khopunov, V. I. Revnivtsev

The process of triboelectric separation from the point of view of its potential for selective separation of various mineral particles can be described as "dry flotation." Large scale practical applications of this technique are limited because suitable models which can describe contact charging of mineral particles have not been developed. Among the various concepts a promising one is an attempt to change development in dielectric minerals within the limits of contact phenomenon in semiconductors. Experimental investigations reported in this paper indicate that the charge development is mainly a result of contact electrification of dielectric minerals characterized by "donor" and "acceptor" type energy spectra due to lattice defects.

Jan 1, 1980

By A. J. Lynch, N. W. Johnson, D. J. McKee

The behavior of nonsulfide gangue in chalcopyrite flotation circuits has been investigated. Plant and laboratory tests were conducted on five different ores. Linear relationships between the recovery rates of free nonsulfide gangue and water were observed. From pilot plant tests, there was evidence that the linear relationship was actually a linear approximation to a parabolic relationship. There was evidence that free nonsulfide gangue is transported from the pulp to the froth in the water and that the gangue is subjected to hydraulic classification in the froth column. A classification matrix has been proposed to define this behavior. This matrix is suitable for inclusion in a mathematical model of the process.

Jan 1, 1975

By S. L. Crouch

The application of a simple, two-dimensional computer technique for evaluating rock burst potential in cut-and-fill stopes was investigated. The principal purpose of the study was to compare the effectiveness of high-modulus fill and destressing as aids in the control of rock bursts. Two conclusions that are probably of general applicability are drawn. First, high-modulus fill is ineffective as a means of increasing the mine stiffness and acts to control rock bursts only if it supports enough load to reduce substantially the stresses on the unmined vein material. Second, destressing is most effective if it is performed when the vein material is near the point of failure.

Jan 1, 1975

By J. B. Evans

Maintaining overall optimum profitability at a mine site necessitates constant reassessment of operating strategies. In essence, each strategy is a particular combination of envisaged capital expenditure, income flow and elapsed time. Selecting a strategy, based on profita¬bility potential requires each contemplated strategy being subjected to discounted cash flow analysis; even with a computer such analysis can be cumbersome. The chapter discusses a 'shortcut' technique which assigns profitability rankings to alternate strategies and iden¬tifies those aspects of a. strategy which impact heavily on profitabil¬ity. This technique can yield quick assessments of sufficient accuracy for many operating strategy decisions. taken on site at on-going mines.

Jan 1, 1978

By M. D. Cooper

Production of both anthracite and bituminous coal in 1954 was about 16 pct below 1953. Estimates on Dec. 1, 1954, indicated 27 million tons of anthracite and 385 million tons of bituminous. Decline in production was due principally to lower demand by the steel industry and the railroads, although competition from other fuels also affected coal. The year was notable for vigorous effort by the coal industry to promote the use of its product. A Cabinet Committee on Energy Supplies and Resources Policy and an Interdepartmental Committee on the Soft Coal Industry were set up by the Administration in Washington. A Governors' Fuel Conference was also organized.

Jan 3, 1955

By Douglas Ragland

Two subjects certain to incite interest among a few practicing engineers and almost all engineering educators are professional recognition and decline in engineering enrollments. It is not surprising that this interest on the part of the educators is universal; it is only regrettable that such an interest on the part of the practitioners is not more widespread. In fact, it is probably the hope of the profession that some of the more penetrating searches now being made into the nature of engineering will generate sufficient cause for perplexity that members of the profession will assume a significant degree of personal concern toward purely professional matters.

Jan 1, 1963

By B. K. Parekh, W. M. Goldberger

A novel process is proposed for continuous removal of ash and unreacted solids which become suspended in the oils obtained during coal liquefaction. The proposed method uses water in direct contact with the oil under conditions which cause the suspended residue solids to transfer from the oil to the water phase. Separation of the phases yields a product oil essentially free of suspended solids. The water is cooled, clarified or filtered by conventional low-cost systems, and recirculated. The paper describes experimental work leading to development of the novel concept and includes the result of batch experiments that establish the feasibility of the process.

Jan 1, 1980

By James L. Kelly

Stripping of the Twin Buttes copper deposit started in 1965. Total material removed for the first 10 yr of operation is approximately 879 million tons. The sulfide concentrator has treated about 45 million tons. The Twin Buttes mineral zone was concealed under several hundred feet of recent alluvium. Beneath this post-minera1 cover, Paleozoic limestone, siltstone and quartzite, and Mesozoic metaarqillite, arkose, conglomerate, and volcanic rocks are intruded by an igneous complex of quartz monzonite and diorite. All rock units are erratically mineralized, principally with copper and molybdenum. Strongest copper mineral favors the Paleozoic calc-silicated limestone and siltstone, often preferential to individual beds.

Jan 1, 1978

By Kalanadh V. S. Sastry, D. W. Fuerstenau

A locked-cycle balling procedure has been designed to simulate continuous, closed- circuit balling drum operation in the laboratory. By this method, it is possible to simulate the surging in green-ball production rate and circulating load that is experienced in industrial balling circuits. Through an investigation of the effect of feed rate on the stability of the locked-cycle, balling process, it was found that higher feed rates lead to increasing instability in the process. An analysis of the experimental ,results is presented and the utility of the locked-cycle experimental technique for evaluating the stability of an industrial balling drum operation is discussed.

Jan 1, 1976

By James C. Fisher

Traditional uranium exploration techniques were utilized and comparatively evaluated in the Front Range, Colorado uranium province. Intense surficial leaching and thick colluvial cover render traditional airborne and ground radioactivity reconnaissance prospecting useless. Radon gas emanometry and sulfur gas emanometry were slightly more effective but the long and short term variations In soil gas emanation rates make it extremely difficult to gain useful information from these systems. The technique judged most useful was Track Etch radon prospecting. The excellent definition of the technique, as well as its repeatability, indicate that it is an ideal prospecting tool for narrow vein-type deposits similar to those of the Front Range, Colorado.

Jan 1, 1976

By C. B. Barlow, T. A. Mekelburg

Due to a tight ash constraint on the clean coal product and difficult middlings washability characteristics, a considerable amount of coal was being lost in the jig middlings at the Monterey No. 2 Mine. An investigation was conducted into circuitry to recover this lost coal with minimal effect on the total clean coal ash. A reverse two-stage hydrocyclone system cleaning at low specific gravities was selected. This system is currently recovering approximately 5.8 kg/s (23 stph) of 11.5% to 12.5% ash coal. The specific gravity of separation for the system is about 1.5 and the probable error is 0.13.

Jan 1, 1986

By R. C. Croft

Many chemical methods of upgrading ilmenite to enhance its titanium dioxide content involve reduction of the FeO in this mineral followed by solution of the metallic iron produced. While the use of most mineral acids for this purpose entails acid regeneration or salt disposal problems, these difficulties can be overcome with carbonic acid. Satisfactory rates of iron removal have been achieved at temperatures below 100° C and at CO, pressures up to 600 psi. Lowering of gas pressure over soluble bicarbonate solutions permits recovery of CO. and precipitation of iron oxide. The removal of the manganese, often present in ilmenites, is also feasible with these treatments.

Jan 1, 1972

By M. D. Scott

A second generation tailings system, consisting of 8 km (5 mile) of large diameter 914- mm (36-in.) po1yethylene pipeline, the bulk of which was laid on a 0.2% grade, has been successfully operated by Lornex Mining Corp. for the past 2 yr. The system was designed to operate as a partial flow pipeline during average flows with the ability to pressurize itself and operate as a pressure pipeline under high flows, or clean itself out under sanding conditions. The system has exceeded design capacity and has had very little downtime. Polyethylene pipe was easily and inexpensively installed and has exhibited superior abrasion resistance characteristics.

Jan 1, 1978

By T. D. Yensen

IF the question should be asked at this time: "Does pure iron have allotropic transformations?" the reply would necessarily be, "We do not know." And it is doubtful whether anybody, anywhere, is in a FIG. 1.-EFFECT OF CARBON ON HYSTERESIS LOSS OF IRON-SILICON ALLOYS. (ALL OTHER IMPURITIES AND EFFECT. OF GRAIN SIZE ELIMINATED.) position to make any other reply at this time, for the simple reason that pure iron has not yet been made and tested. The nearest approach to it contains either an appreciable amount of carbon or else an appreciable amount of oxygen (a few hundredths of a per cent.). But why be con-

Jan 1, 1929

By William Kent

A MOST startling and as yet unexplained, failure of steel boilerplates, in two different sets of boilers, is reported in a paper by Arthur J. Maginnis, published in the London Engineer, December 11th, 1885, and reprinted in the American Engineer, January 14th, 1386. The facts of the case, as condensed from Mr. Maginnis's paper and from a number of letters in the subsequent issues of the Engineer, are as follows: 1. The material used for two different sets of boilers on two different steamers, each set consisting of three circular boilers with horizontal steam-chests, passed all tests required by the Board of Trade

Jan 1, 1886

By William Braden

IT is obvious that the choice of the method to be employed in the handling of blast-furnace slags and mattes depends upon local facilities and conditions which may indicate as advisable some particular plan. As a result of the variety of such conditions hardly any two smelters use identically the same method, though they be located only a few hundred feet apart. For instance, of the several plants in Leadville, Colorado, each has a more or less distinctive system. The same is true of Salt Lake City and vicinity. In view of this it is evident that the existing diversity of practice cannot be accepted, prima facia, as evidence

Jan 1, 1897

By M. S. Enders, L. M. Rogers

The Little Rocky Mountains host epithermal gold-silver bearing vein and stockwork deposits in a syenite intrusive complex. Pegasus Gold Ltd. is currently mining these oxidized deposits by open-pit methods and recovering gold and silver by heap-leach processes. A geologic program has been designed to effectively determine the basic ore characteristics; 1) mineralization; 2) oxidation; 3) structural setting; 4) lithology; 5) alteration; and ultimately, 6) the leachability of the ore. Geologic mapping, sampling, drilling, assaying, and testing are routinely used in exploration, development, production control, mine planning, and ore reserve estimations. Timely and accurate assay results are essential for the program's success.

Jan 1, 1984

By Craig R. Smith, Warren Pfefferle

Tests were conducted utilizing large flat jack devices placed in a vertical slot for high pressure loading of rock to measure in-situ properties of a rock mass. The high pressure flat jack devices were used as a site investigation tool to obtain rock mass properties. Tests were conducted before and after a 100 ton surface high explosive detonation test to assess explosive effects on the rock. It was conclusively demonstrated by these tests that meaningful flat jack tests could be successfully accomplished; also, a significantly different response of the rock medium was measured as larger areas of rock were loaded. Surface jointing was severely disturbed by the explosion.

Jan 1, 1971

By S. L. Tainter

This paper describes the nature of engineering and geologic services for the production stage and a review of pit design factors peculiar to the development period. The Mission pit has passed into the mining phase where development is of secondary importance; however: until the pit reaches its final size, development will be a continuing function occurring simultaneously with mining operations. The deposit occurs in an extensive zone of altered sedimentary rocks which have been fractured by three fault systems, flexed or folded, and intruded by monzonite porphyry. The deposit is a low-grade copper sulfide "porphyry" type orebody within a broad zone of pervasive hydrothermal alteration in sedimentary rocks.

Jan 12, 1965

By F. F. Aplan, E. C. Dowling, R. R. Klimpel

Numerous flotation models have been proposed in the literature. Thirteen of these have been applied to batch flotation data and evaluated with respect to one another using statistical techniques. Flotation tests were carried out on samples of a US porphyry copper ore (Pinto Valley, AZ). The ore was tested using various collector and frother systems to produce different time-recovery profiles. These were used to calculate flotation rate and ultimate recovery parameters for each model. The models were then evaluated statistically to determine the overall fit of the calculated to the observed data and to test the range of significance of the parameters in each model.

Jan 1, 1986